The present disclosure is related to equipment used in conjunction with operations performed in subterranean wells and, more particularly, to corrosion and wear resistant casing joints for a well junction.
Hydrocarbons can be produced through a wellbore traversing a subterranean formation. The wellbore may be a multilateral wellbore that includes a main or parent wellbore and one or more lateral or sidetrack wellbores that extend from the parent wellbore. Typically, once casing string is installed in the parent wellbore, a whipstock can then be lowered into the wellbore and positioned within the casing string at a desired location where a lateral wellbore is to be drilled. One or more mills are then advanced to the whipstock and deflected laterally to penetrate a casing joint arranged within the casing string, thereby forming a window through which a drill bit can form the lateral wellbore.
Casing joints are often made from high-strength materials that are non-corrosive and otherwise able to withstand corrosive downhole fluids that may be present in the subterranean environment, such as hydrogen sulfide and carbon dioxide. Milling the window through such high-strength materials, however, can be difficult and generate debris and/or cuttings that may prevent the whipstock from being retrieved after the window is properly milled into the casing joint. Such debris and/or cuttings may also plug flow control devices, damage seals, obstruct seal bores, and interfere with positioning components in the parent wellbore below the casing joint.
Casing joints with pre-milled windows are sometimes used to reduce or eliminate debris, but typically must include a liner or sleeve to prevent wellbore particulates from entering the inner diameter of the casing string during installation. While the liner can be made of fiberglass, which can be milled easily and result in less debris as compared to drilling through a casing joint made from a high-strength material, fiberglass liners can be susceptible to failure under the high pressures present in the subterranean environment. Accordingly, additional support in the form of an aluminum sleeve may be desired. Aluminum sleeves, however, can prematurely wear while the parent wellbore is being drilled, and the aluminum material may further be susceptible to galvanic corrosion when coupled to steel portions of the casing string. More particularly, the aluminum material may act as an anode when in galvanic contact with steel and generally has lower corrosion and wear resistance than steel.